The combination of a cathodic arc discharge and an unbalanced magnetron for the coating of tools and components which are subjected to severe wear is disclosed in U.S. Pat. No. 5,306,407 Hauzer et al, and in W.-D. Münz, C. Schöhnjahn, H. Paritong, I. J. Smith, Le Vide, No, 297, Vol. 3/4, 2000, p. 205–223 and has proved to be very successful when employed industrially (see W.-D. Münz, I. J. Smith, SVC, 42 Ann. Tech. Conf. Proc., Chicago, Ill., Apr. 17–22, 1999, p. 350–356)
The multiply-ionised metal ions which are produced in the vapour of the cathodic arc discharge are used for low-energy ion implantation; typical acceleration voltage at the substrate: 1.2 kV, in order to produce ideal conditions for excellent layer bonding. In special cases, localised, epitaxial layer growth can even be achieved (see C. Schöhnjahn, L, A. Donohue, D. B. Lewis, W.-D. Münz, R. D. Twesten, I, Petrov, Journal of Vacuum Science and Technology, Vol. 18, Iss. 4. 2000, p. 1718–1723).
Bombarding the substrate surface with Cr ions has proved to be particularly successful as described in U.S. Pat. No. 6,033,734 Münz et al, since firstly excellent bonding strengths are achieved and secondly the macro-particles (“droplets”) which are formed as an unwanted by-product have proved to be small compared with the macro-particles which are formed during cathodic arc discharge from materials with a lower melting point, e.g. Ti or TiAl (see W.-D. Münz, I. J. Smith, D. B. Lewis, S. Creasy, Vacuum, Vol. 48, Issue. 5, 1997, p, 473–481).
Whereas in many applications of tool coating these macro-particles, which develop into considerably enlarged growth defects during coating with an unbalanced magnetron, are only of secondary importance, they become considerably more important in anti-corrosion applications (see H. W. Wang, M. M. Stark, S. B. Lyon, P. Hovsepian, W.-D. Münz. Surf, Coat. Technol., 126, 2000, p. 279–287) or during the dry machining of hardened steels (HRC-60), for example, where layer roughness and porosity play a significant part.
With regard to the processes used in the field of industrial PVD coating, it has hitherto only been practicable to produce high metal ion densities by means of a cathodic arc discharge. On the other hand, the importance of magnetic-field assisted pulsed cathode sputtering is increasing appreciably.
By using power densities higher than 1000 W.cm−2, it is possible to produce metal vapours in which up to 60% of the metal atoms are ionised (see A. P. Ehiasarian, R. New, K. M. Macak, W.-D. Münz, L Hultman U. Helmersson, V. Kouznetsov, Vacuum, 65 (2202), p 147. This value is comparable with the degrees of ionisation of metal vapours achieved in a cathodic arc discharge.